During the reporting period A. Leith was involved in maintenance and improvements to the SPIDER & WEB systems for image processing and image analysis. SPIDER was improved by adding new operations such as "IF...THEN" for control of batch processing and file-name substitution. In addition "stacks" of SPIDER images can now be created within the same file or within an "inline file". These changes are especially important now that some users are creating reconstructions from more than 10,000 images. Operations involving Fourier transformations were speeded up 2-3 fold. The operations for conversion between SPIDER format images and other standard image file formats were rationalized and improved. Also the communication between SPIDER and the underlying operating system was improved by modifying the "VM" operation and establishing control of the number of processors utilized on multi-processor systems. Considerable effort was spent on improving SPIDER documentation, especially checking for errors or omissions. The "SPIDER Users Guide" was improved with the addition of new material and the short descriptions of all SPIDER operations were updated.